Large turbine generators are constructed in which a coolant gas, usually hydrogen, is circulated through ducts in the stator and rotor slots in direct thermal relation with the current-carrying conductors inside ground insulation. These type of systems are disclosed in commonly assigned U.S. Pat. Nos. 3,110,827; 3,265,912; and 4,751,412. Cooling is accomplished by dividing the air gap formed between the rotor and stator core transversely into a plurality of annular zones by positioning baffles in annular rings in the air gap. These baffles are mounted on the stator core, which oppose rings on the rotor. Typically, there are about five to about eight circumferentially extending baffle rings or groups of baffles that form alternate cooling zones, which are connected to the high pressure, or discharge side of blower, typically mounted on the rotor shaft. Any remaining cooling zones are connected to the low pressure or entrance side of the blower. Radial ducts or passages in the rotor in each cooling zone permit the cooling gas to flow from the high pressure zones to low pressure zones and through longitudinal ducts of the rotor winding. This pressure exerted by the blower forces the gas through rotor ducts in short axial paths to obtain adequate gas flow.
The baffles arranged on the stator core typically are configured to form about a 0.060 inch gap between the two, which prevents gas flow between the baffles and cooling zones. The baffles also must be formed to maintain their position without lateral movement and thus maintain the integrity of the cooling zones. The stator baffles must be removable even when the rotor is in place, as explained in the above-identified and incorporated by reference patents. For example, the '912 patent teaches the use of annular stationary baffles positioned in a ring along the bore of the stator core. These baffles align radially with the baffles of the rotor. Each stationary baffle train is formed as segmented baffle segments, each having a baffle base disposed in a slot of the stator core. The baffle segments are interconnected in a longitudinally extending baffle train. For example, the baffles disclosed in the '912 patent include a row of longitudinally spaced baffle segments and held together end-wise with steel cables. Abutting the ends are spacers, and the bases of baffle segments are oppositely tapered, forming a compressive load applied end-to-end. Steel cables extends from one end of the row to the other end and placed under tension to wedge this assembly or baffle train into place. This type of approach creates cable and tensioning problems. For example, the cable is often stretched and major repairs are required. Additionally, the entire “train” of baffles must be inserted or withdrawn as one unit and placed on a tray for storage or service, which can be time-consuming and expensive.
The '412 patent discloses another “baffle” system using a “train” of camlocked air gap baffles and an improved method of installing baffles within the stator of large gas-cooled dynamoelectric machines (gas-cooled turbine generators) using segmented baffles spaced by insulated tubes. Each baffle includes a lower, tapered wedge and upper transverse member. The “train” includes a very long tube or other support having a number of rotatable cams that are positioned on the tube to engage and expand the wedge against the stator slot and lock the baffle in place. The entire baffle train for a stator must be inserted or removed when only one baffle is inserted or replaced. Also, the longitudinally extending tubes are prone to torsion and twist, and thus, some wedges and baffles may lock while others may not lock properly.
It would be advantageous if a system method for installing air gap baffles configured in segmented baffle rings could be accomplished without using long baffle “trains,” which add complexity during installation, increase repair time and costs, and decrease the durability of the component parts in service.